Module io.jenetics.ext

Package io.jenetics.ext.grammar

Class SentenceGenerator<T>

java.lang.Object

io.jenetics.ext.grammar.SentenceGenerator<T>

All Implemented Interfaces:

Generator<T,List<Cfg.Terminal<T>>>

public final class SentenceGenerator<T>
extends Object
implements Generator<T,List<Cfg.Terminal<T>>>

Standard implementation of a sentence generator. The generator can generate sentences by expanding the grammar in a SentenceGenerator.Expansion.LEFT_MOST or SentenceGenerator.Expansion.LEFT_TO_RIGHT order.

The following code snippet shows how to create a random sentence from a given grammar:

final Cfg<String> cfg = Bnf.parse("""
    <expr> ::= ( <expr> <op> <expr> ) | <num> | <var> |  <fun> ( <arg>, <arg> )
    <fun>  ::= FUN1 | FUN2
    <arg>  ::= <expr> | <var> | <num>
    <op>   ::= + | - | * | /
    <var>  ::= x | y
    <num>  ::= 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
    """
);

final var random = RandomGenerator.of("L64X256MixRandom");
final var generator = new SentenceGenerator<String>(
    SymbolIndex.of(random),
    1_000
);
final List<Terminal<String>> sentence = generator.generate(cfg);
final String string = sentence.stream()
    .map(Symbol::name)
    .collect(Collectors.joining());

System.out.println(string);

Some sample output:

 > ((x-FUN1(5,5))+8)
 > (FUN2(y,5)-FUN2(0,x))
 > x
 > FUN2(x,x)
 > 5
 > FUN2(y,FUN2((FUN1(5,FUN1(y,2))*9),y))
 > ((FUN1(x,5)*9)*(x/(y*FUN2(x,y))))
 > (9-(y*(x+x)))
 >
 

Since:

7.1

Version:

7.1

See Also:

• DerivationTreeGenerator

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static enum	SentenceGenerator.Expansion	Defines the expansion strategy used when generating the sentences.

Constructor Summary

Constructors

Constructor	Description
SentenceGenerator(SymbolIndex index, int limit)	Create a new sentence generator from the given parameters.
SentenceGenerator(SymbolIndex index, SentenceGenerator.Expansion expansion, int limit)	Create a new sentence generator from the given parameters.

Method Summary

Modifier and Type	Method	Description
List<Cfg.Terminal<T>>	generate(Cfg<? extends T> cfg)	Generates a new sentence from the given grammar, cfg.
static String	toString(List<? extends Cfg.Symbol<?>> sentence)	Converts a list of symbols to a string, by concatenating the names of the given symbols.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.jenetics.ext.grammar.Generator

map

Constructor Details

SentenceGenerator

public SentenceGenerator(SymbolIndex index,
 SentenceGenerator.Expansion expansion,
 int limit)

Create a new sentence generator from the given parameters.

Parameters:

index - the symbol index function used for generating the sentences

expansion - the sentence generation strategy to use for generating the sentences

limit - the maximal allowed sentence length. If the generated sentence exceeds this length, the generation is interrupted and an empty sentence (empty list) is returned.

SentenceGenerator

public SentenceGenerator(SymbolIndex index,
 int limit)

Create a new sentence generator from the given parameters.

Parameters:

index - the symbol index function used for generating the sentences

limit - the maximal allowed sentence length. If the generated sentence exceeds this length, the generation is interrupted and an empty sentence (empty list) is returned.

Method Details

generate

public List<Cfg.Terminal<T>> generate(Cfg<? extends T> cfg)

Generates a new sentence from the given grammar, cfg.

Specified by:

generate in interface Generator<T,List<Cfg.Terminal<T>>>

Parameters:

cfg - the generating grammar

Returns:

a newly created terminal list (sentence), or an empty list if the length of the sentence exceeds the defined sentence limit

toString

public static String toString(List<? extends Cfg.Symbol<?>> sentence)

Converts a list of symbols to a string, by concatenating the names of the given symbols.

Parameters:

sentence - the symbol list to covert

Returns:

the converted sentences